This is what I came up with while making my own NBT. The entire trip assembly can be removed from the "trap house" for maintenance, or if your on vacation and can't monitor it daily. ALL TRAPS MUST BE MONITORED DAILY. I found that while making this, some basic things apply. The lightest materials, and the shorter you design the lever, will trip with less weight. I had this completely finished; painted the inside of the plastic jug to darken the "nest area" and had to re-adjust the weight! The weight of painting the jug, changed the sensitivity. Most traps like this strive to trip with the weight of 5 to 7 quarters (coins) this one will trip on 1 quarter & a dime. Fifty cents (2 quarters) will trip this every time by gently laying the coins in; not tossing! The brass hinge keeps side to side play to a minimum, reducing any hang-ups.

The foundation (fulcrum) can be made of anything. 2 and 5/8 inches tall is what it takes to "travel" up and down the distance of the diameter of the entrance & exit hole. When a Starling or House Sparrow (S&S) jumps in, the nest box must fall 2-1/4" to block the entrance. The S&S will have only one choice to get out; the exit hole to your 4" pipe mounted on the back of your trap, and then down to the holding cage, live & unharmed.

Photo Above Left. When mounting the brass hinge, make sure the "barrel" of the hinge does not rub the foundation you mount it to . Notice how I have mounted this hinge slightly above the angle so that there are no points of contact that could cause "sticking".

Mount Hinge at 2-5/8" from center of hinge to base. The angle "foundation", or the "fulcrum" shown here, is 2-3/8" tall. You will need it so the jug will drop far enough down to cover the entrance hole to the trap. This measurement is critical. Maximum 2-¾,

Minimum of 2-½ inches.

Photo Above Right shows how the hinge is almost too large for the angle. Although this looks tacky, I chose the smallest (lightest) lever. 1inch aluminum angle, about 1/16" thick. I also wanted a good size brass hinge to provide the least amount of friction, and minimize side to side play so the jug does not make contact with the walls of the house. Minimizing a trap that is stuck in an "up" or "down" position.

Photo Above Left. Centerline of pin on hinge, to counterweight is just under 3-¼ inches.

Photo Above Right. Centerline of pin on hinge, to center of nest area - 5 inches.

Stay as close as you can to these measurements. Altering these, affects how sensitive the trap is.

I made the entire trip assembly as short as possible because the lighter you build it, the less weight it takes to trip it. It can be used to catch lighter House Sparrows. Also a shorter house to be built around it. I have found it is easier to build a trip assembly first, then a build your Nest Box Trap (birdhouse) around it.

Photo Above Left shows the adjustable wood screws in the 1x 8 x 13 base. Inside dimensions on my Western Red Cedar birdhouse boxes are 8"X 14"X 10" tall. These screws are to keep the trip assembly set precisely in the birdhouse box, so when you remove the assembly to clean poop out of the jug (which will change the balance) it will line up exactly where you pre-set it to be. Start by running the screws in fairly deep. Put the assembly in the bird house box, and see which way to lengthen or shorten the screws to keep the assembly exactly where you want it. Small spacers at the bottom of the box, where the screws will hit, will prevent the screws from rubbing the entire wall of the box when lifting out the trip assembly. You'll see what I mean when you get to this step.

Photo Above Right. Notice the jug I selected. Light, plastic. I get these from restaurants. This is a 1 gallon container. The top of the jug is facing forward, and is the entrance side of the trap. By cutting your jug this way, the top of the entrance hole is 7" instead of 9 inches. This is very nice when building your house. The entrance hole to the trap is not "crammed" up to the top. It is 2" lower. By using the jug cut this way; a Starling looks inside and finds a nice large cavity. All he sees, is a nice big room; tall as it is wide. 2 inches in height is saved by this style entrance to your jug. The jug only needs to drop far enough to cover the entrance hole. Paint the top of the jug white, so you can tell if it needs to have poop and junk cleaned out. This excess weight, built up over time, will need to be cleaned out.

Photos Above. Cut entrance hole on birdhouse box, as far to the right as possible. This must be done so when the bird jumps in, the entrance hole he came in is completely covered. Some birds have been able to turn around, see a gap, and pry the jug back up and escape. Make sure your entrance hole is covered completely when the jug drops.

Photo Above Left. The roll of teflon tape (size of exit hole) represents the exit hole. When the Starling or Sparrow jumps in, the trap falls to line up with the exit hole.

Locating Holes on Bird Box. (read instructions in photo above right) Do not drill anything until you have tested your trip assembly inside your birdhouse box. I adjust my trip assembly to be as far to the right of the box as possible and still not touch the walls when moving assembly up and down. This way, the entrance hole on my birdhouse box is as far to the right as possible, and the other "fake holes" drawn on the box, are space out nicely. Again, fit assembly in box, and adjust BEFORE you cut entrance & exit holes.

Trim your jug so you have a slight gap between the walls and the plastic jug.

When drilling "locater holes", drill the small holes inside where you think the 2-1/8" entrance and exit hole will be. With the drill bit through the wall you can see where the edge of you 2-1/8" hole should be. Use the small hole you drilled and mark where you want the edge of your hole with a pencil. When you use your hole saw drill, align the edges of the hole saw bit with the lines you drew on the box. Plan on these small locater holes to "land inside" your 2-1/8" entrance and exit holes. If they don't, it will just be "cosmetic" and will not affect your Nest Box Trap.

Photo Above Left is another "shot" of locating the entrance hole. Take an educated guess on where you think the 2-1/8 entrance hole will be. Then use a small drill to make sure you are correct.

Photo on Right, shows the entrance to the trap. Look inside the hole and you can see the edges of the jug. The entrance hole is located as far to the right, and as high as possible, so when the trap falls, the entrance hole is covered by the top of the jug.

Photo Above Left. Notice the 50 cents holding the jug down. This is the back of the "bird house" where the " down chute " will be placed. I have drawn lines representing where the jug is. Once again, this is the back, or the exit.

Photo Above Right. Notice the counterweight. Stack washers to adjust the balance. The 3-¼" bolt is also the "Up Position Stop". Jug drops when bird jumps in; counterweight pulls it back up; and the bolt stops the trap at a height you choose. Mount hinge on the heavy side of the fulcrum. You want the "jug side", as light as possible.

Photo Above Left shows the trap inside the "bird house" (RV battery case). Trim the jug to only have about 1/8" to 1/4" space from the walls. The wood screws in the base is to adjust the jug center line. Once you adjust, the trap can be taken out and dropped right back in; lined up perfectly. (I now use a large cooler for my plastic versions.)

Photo on Right, shows the trap in the "tripped" position. I placed 2 quarters (coins) inside to keep it down. This shows the top of the jug is lower than the entrance hole. The bird has only one choice out. The exit hole. Entrance hole MUST be out of a trapped birds reach. I had to add the slick surface of the plastic, so the bird could not climb out.

Photo Above Left shows proof it works! I used an old hamster cage as a holding pen. Notice the finished trip assembly. Paint the inside black, so a sneaky starling will go in.

Photo Above Right shows how this trap is placed close to trees where Purple Martins are not interested. The branches on the Cedar trees are only a foot or two from the NBT. When a NBT is placed close to martin housing with Starling Resistant Entrance Holes (SREH's), it is much more effective. The NBT only catches birds looking for nest sites. When Starlings are trying to gain access to your SREH's on your martin housing, and they see this other bird box with large round holes, it is hard for them not to pass up peeking inside this "birdhouse". I rarely catch any native birds in this trap. Purple Martins aren't interested in it, because it is too close to trees. If you have a problem catching Bluebirds, simply put an 1-½" hole on the cage. BUT…this will allow smaller House Sparrows to exit also. Monitor your trap hourly. If you catch a native bird, simply release it.

Photo Above Left is a front view of a NBT in my yard. This is made of Western Red Cedar. Only 1 black circle is a hole. The rest are fake's drawn on with a black marker. A Starling will see the holes as a house to steal a nest from. Top Right circle is the entrance. The 4 inch sewer pipe (chute) is tucked neatly behind the 4x4 post by using a 22-1/2 degree bend. By using this slight bend, the first part of the chute is close enough to vertical to keep the bird from clinging to the pipe and defeating the trap.

Photo Above Right shows a way you can attach a 4 inch sewer pipe to the box. Just two small wood screws hold this on. Using a 2 inch hole saw, drill a hole 6 inches from the top end of the pipe. A bird caught in the trip assembly, will look out the exit hole, and see freedom directly across the pipe to the 1-¼" hole. The bird will also see 1-¼" holes in the cap above, and will want to try to get out by jumping in the pipe to gain access to the holes in the cap or the one directly across from the exit hole. They can't grasp the slick, interior surface of the pipe -- Can't open their wings far enough to fly in the 4 inch sewer pipe, and just fall down to the holding cage. …..(See photos of exit chute on above.)

Photo Above Left shows how my holding pen is set-up. When I need to cut the grass, I remove my cage by lifting the 4 inch sewer pipe and taking the piece of wood out from under it. Then the pipe can slip out of the 22-1/2" degree bend, and everything can be moved without any tools. I store as much of this inside during the winter as I can.

Photo Above Right has a lot of information in it. This was the first thing I came up with on my holding pen, and it has worked well, but I did improve the opening since this photo was taken. Just make a cage that a bird cannot escape from. The nice thing about the NBT is that to disable the trap, simply leave this cage door open. Birds in the cage are live and unharmed, but NEED TO BE MONITORED HOURLY, or disable by leaving the cage open.

I am no longer making wood NBT's. If you choose to make one with wood, paint it white. Woodpeckers and squirrels seem to be lured to the natural wood. I wanted to make one that is maintenance free. The Western Red Cedar holds up okay, but not when a squirrel or woodpecker wants in. I am presently making one of aluminum.

Roof.

Many different ways to make a roof for your trap. As long as your roof lets you access the trip assembly, and keeps the inside dry, that is all you need.

How the NBT works:

When the bird jumps in the nest box trap, and the bottom drops, this scares the bird and it immediately wants out. On this trap, he looks out the 2 1/8" hole in the back of the house and sees daylight through the 4" sewer pipe, by looking across the pipe at the 1-¼" hole, and four 1-¼" holes drilled in the top of the pipe cap. A Starling will only get his head out of the hole. His wings won't hold him up flapping inside the pipe. No bottom, so he falls to the bottom of the 4 inch pipe into the hamster cage. I can use binoculars from my window at home and see if I have anything in my trap. Plenty of room to help keep any birds calm. Good birds get set free. European Starlings and English House Sparrows… do not get set free, but are humanely exterminated.

ALL TRAPS MUST BE MONITORED DAILY. Please don't chance killing native birds. If you don't have time to monitor, close or disable your trap. To disable this trap, I just leave the door on the cage open. Birds still pass through the trap, but are unharmed and just fly out of the open cage at the bottom of the 4" pipe. (chute)

Adding a little grass, sticks or smearing mud inside the jug, will make this trap much more effective. Starlings will jump right in, if they feel like they have found an active nest to steal. Help all native birds in your area by building a NBT.

My brass hinge traps are very sensitive, and will trip on the weight of two quarters. (Coins) You may call this "bragging rights". If you have bought a trip assembly from me, you received it tripping with the weight of 2 quarters. These style traps strive to trip with the weight of 5 quarters. This is about equal to the weight of a small House Sparrow. Starlings are heavier, about equal to the weight of 7 to 9 quarters.

The trap I use at home is still set to lightest "50 cent" setting. You can virtually eliminate all possible hang ups, by adding some washers to your counterbalance. If you are worried about your trap sticking (I don't), you can adjust your trip assembly to reset faster and take more weight to make it go down.

So think about it. If it will trip with the weight of 2 quarters, and you add washers to your counterbalance, the jug will be "pulled" up with the added washers. Set yours to trip with the weight of 3 quarters if this puts your mind at ease. The only problems that I've had with mine is weight added to the jug. Seems like it scares the poop out of Starlings as soon as they enter. Build up of several Starlings going through the trap, adds to the weight of junk in the jug. One time my jug was stuck, and I figured out that it was rain water collected in the jug. I have since drilled drain holes in the bottom of my jug.

Just daily glance at the entrance hole of the trap. If you see the white part of the jug, a bird is in it, or bird poop, stick, mud, and/or grass is in the jug holding it down. I drill a couple of small holes in the bottom of my jug to let rain water escape.

Several Purple Martin Landlords have bought a complete trap from me and have helped me work the bugs out of my version of the Nest Box Trap or NBT. These NBT's work. I don't know how I enjoyed my martin colony without one. Build yourself one from these instructions, or send me an email to find out if I have made any to sell over the winter.

ALL TRAPS MUST BE MONITORED DAILY. Please don't chance killing native birds. If you don't have time to monitor, close or disable your trap.